JPS62249640A - Acoustic lens and ultrasonic probe using composite using thesame - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention mainly relates to an acoustic lens used in an ultrasonic probe of an ultrasonic diagnostic apparatus and the ultrasonic probe.

(Prior Art) In general, acoustic lenses have been conventionally used in ultrasonic diagnostic apparatuses for the purpose of improving the resolution of images obtained. This acoustic lens uses a material whose propagation speed of sound waves (hereinafter also referred to as sound speed) is slower than the sound speed of the living body (■0) as the lens material in order to focus the ultrasonic beam on the living body. The shape is convex as shown in FIG. 4(a), and when a material with a sound velocity v2 faster than the sound velocity VO of a living body is used, it becomes a concave shape as shown in FIG. 4(b). However, as for an acoustic lens for an ultrasound probe used in direct contact with a living body surface, if the surface is concave, the adhesion to the living body becomes poor and good tomographic images cannot be obtained. Therefore, acoustic lenses with convex surfaces are widely used as acoustic lenses for ultrasound probes that are brought into direct contact with the surface of a living body. For an acoustic lens material with a convex surface, the speed of sound must be sufficiently slower than the speed of sound in a living body, and in addition to the speed of sound, the acoustic impedance must be as close as possible to that of a living body, and the attenuation of ultrasonic waves must be small. The following characteristics are required. Currently, as a material for such a convex lens, silicone rubber is widely used because its sound velocity is approximately 1000 m/s, which is sufficiently lower than the sound velocity of a living body (approximately 1530 m/s), and whose acoustic impedance is close to that of a living body.

(Problem to be solved by the invention) However, silicone rubber has a considerably high attenuation, for example, an ultrasonic wave with a frequency of 5 and 2 has an attenuation of 1! Iu! This results in attenuation of 3 to 4 d8 per unit, which is one of the causes of deterioration of the S/N of ultrasonic diagnostic equipment. In addition, silicone rubber has a high permeability of moisture, and moisture can enter the inside of the ultrasound probe through the silicone rubber, causing deterioration of internal materials such as the transducer, which is one of the causes of deterioration of the sensitivity of the ultrasound probe. ing.

The purpose of the present invention is to solve the problems of the prior art as described above, to provide an acoustic lens having the characteristics of low attenuation of sound waves and low moisture transmission, and to further use this acoustic lens in ultrasonic diagnostic equipment. By applying the present invention to a sonic probe, the present invention aims to provide an ultrasonic probe that has an improved S/N ratio, is easy to use, and has excellent long-term reliability.

[Structure of the Invention] (Means for Solving the Problems) A composite acoustic lens according to the first invention includes a convex first lens made of a material in which the propagation speed of sound waves is slower than the propagation speed in a living body.
A converging acoustic lens and a concave second converging acoustic lens made of a material whose propagation speed of sound waves is faster than the propagation speed in the living body are constructed by joining the convex surface and the concave surface and integrating them into a composite body. There is.

Moreover, the ultrasonic probe according to the second invention is configured by disposing the composite acoustic lens according to the first invention on the wave transmitting/receiving surface side of the ultrasonic transducer.

(for production) Since the present invention has the above configuration, it operates as follows.

That is, the first converging acoustic lens made of a material whose sound velocity is slower than that of a living body has a convex shape, and the second converging acoustic lens made of a material whose sound velocity is faster than that of a living body has a convex shape. has a concave shape. Therefore, by combining the concave and convex surfaces of both lenses, it is possible to form one substantially flat composite acoustic lens (hereinafter also abbreviated as a composite lens). In this case, the first
Second, since both lenses have a convergence effect, the thickness of one composite lens becomes small, which reduces the attenuation of ultrasonic waves. In addition, since there are waterproof materials such as plastics, which form the second converging lens and whose sound speed is faster than that of a living body, a compound lens made by combining this second converging lens is , moisture permeation can be reduced.

In addition, the ultrasonic probe using such a compound lens has a good S/N ratio because the ultrasonic attenuation of the compound lens is small.
In addition, since the lens surface is almost flat, it adheres well to the body surface and is easy to use, and the second converging acoustic lens of the compound lens is waterproof, preventing moisture from entering the inside of the ultrasound probe. This does not cause deterioration of the internal materials such as the vibrator, and therefore provides excellent long-term reliability.

(Example) The illustrated embodiment will be described below.

An embodiment of the composite acoustic lens according to the first invention is shown in FIG. In this embodiment, the present invention is applied to a cylindrical lens, and its structure is a combination of a convex lens and a concave lens, as shown in FIG. 1(b). Reference numeral 10 denotes a first converging convex lens made of a material (for example, silicone rubber) whose sound speed is slower than that of a living body, and 11 a first convex lens made of a plastic material (for example, TPX) whose sound speed is faster than that of a living body. This is the second concave converging lens. Each lens acts as a converging lens even when used alone. The characteristics obtained by combining these two lenses will be described below in comparison with the case of using each lens alone.

Now, with silicone rubber (velocity of sound Vl = 1000 m/S), focal length F = 6071 in vivo (velocity of sound Vo z1530'rrL/S)! When a single lens with an aperture D=15m is constructed to converge the ultrasound beam on I11, the curvature R1 of this lens is R1=(1-V1/Vo)F=0.34F, so R1
= 20.4s, and the thickness difference dl of the lens is dx = Rt -1-D/2)2, so d1 = 1.43m.

On the other hand, when constructing a single converging lens for the same purpose with a plastic lens, the sound velocity V2; 200OTrt/S
When using a plastic (for example, TPX), its curvature R2 is R2 = (1-vo /V2)F = 0.25F.
2=15m. Therefore, the depth d2 of the recessed valve is d2=R2-2-/2'', so d2←35.4, and the thickness of the lens is d=
It will be 0.8m. Therefore, in this case, the attenuation of the ultrasonic waves in the central portion is 4.8 to 6.4 dB at 58H2, which is 3.8 to 5.1 dB less than a lens made of silicone rubber alone.

FIG. 2 shows an example of an ultrasonic probe using this compound lens.

Reference numeral 1 denotes the above-mentioned compound lens, which is attached to the tip of the probe body 2. As shown in FIG. 3, the compound lens 1 has a flange 12 formed on a second concave convergent lens 11 made of plastic material, and this flange 2 engages with the tip of the probe body 2. This ensures that the probe is mounted securely, and by arranging the plastic second concave converging lens 11 on the outside, it is possible to more reliably prevent water from entering from the outside of the probe. 3 and an ultrasonic transducer disposed on the back of the composite acoustic lens 1, and the ultrasonic transducer 3 has an electrode 5 and a ground electrode 6 for driving it by applying a voltage thereto.
It is equipped with Reference numeral 4 denotes a backing material disposed on the back of the ultrasonic vibrator 3, and is adapted to absorb ultrasonic waves directed toward the back of the vibrator 3.

The above-described compound lens and ultrasonic probe have the following effects. That is, (1) the compound lens of this example has the first. 2nd both lenses 10.
The 11 uneven surfaces are combined into a single flat shape. Since both the second lenses 10 and 11 have a convergence effect, the thickness d of one composite lens becomes small, thereby reducing the attenuation of the ultrasonic waves.

(2) Furthermore, since the second converging lens 11 is made of waterproof plastic, the permeation of moisture can be reduced.

■ Therefore, an ultrasound probe using such a compound lens 1 has a good signal-to-noise ratio because the ultrasonic attenuation of the compound lens is small, and also has good adhesion to the body surface because the shape of the lens surface is flat. It is easy to use, and the second converging acoustic lens 11, which is a compound lens, is waterproof and does not cause moisture to enter the inside of the ultrasonic probe 7 and cause deterioration of the internal materials of the transducer 3, etc., and can be used for a long time. It has excellent reliability.

Furthermore, since the second converging lens 11 is placed outside,
It is possible to more reliably prevent water from entering the probe from outside.

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above embodiments, and can be modified as appropriate within the scope of the gist of the present invention.

For example, the shape of the compound lens is not limited to a flat shape, but can also be a somewhat convex shape.

[Effects of the Invention] As described in detail above, the compound lens of the present invention has a small thickness, so the attenuation of ultrasonic waves is small, and the size of the A4 width is smaller than 5 mm.

(G) Vri V2 < VO (b) Figure 4

Claims (3)

[Claims] (1) A convex first focusing acoustic lens made of a material in which the propagation speed of sound waves is slower than that in the living body, and a concave first converging acoustic lens made of a material in which the propagation speed of sound waves is faster than the propagation speed in the living body. A composite acoustic lens characterized in that the second converging acoustic lens is integrally formed by joining the convex surface and the concave surface. (2) An ultrasonic transducer equipped with an ultrasonic transducer that transmits ultrasonic waves toward a living body and receives reflected echoes thereof, and an acoustic lens disposed on the wave transmitting/receiving surface side of the ultrasonic transducer. In the acoustic probe, the acoustic lens includes a convex first lens made of a material in which the propagation speed of ultrasonic waves is slower than the propagation speed in the living body.
A converging acoustic lens and a concave second converging acoustic lens made of a material whose propagation speed of sound waves is faster than the propagation speed in a living body are integrated by bonding the convex and concave surfaces. An ultrasonic probe characterized by comprising: (3) The ultrasound probe according to claim 2, wherein the first convergence acoustic lens is disposed on the ultrasound transducer side, and the second convergence lens is disposed on the living body contact surface side. .